Israeli shelling and airstrikes killed at least 37 people, most of them sheltering in tents, outside the southern Gaza city of Rafah overnight and on Tuesday — pummeling the same area where strikes triggered a deadly fire days earlier in a camp for displaced Palestinians — according to witnesses, emergency workers and hospital officials.

The tent camp inferno has drawn widespread international outrage, including from some of Israel’s closest allies, over the military’s expanding offensive into Rafah. And in a sign of Israel's growing isolation on the world stage, Spain, Norway and Ireland formally recognized a Palestinian state on Tuesday.

The Israeli military suggested Sunday's blaze in the tent camp may have been caused by secondary explosions, possibly from Palestinian militants' weapons. The results of Israel's initial probe into the fire were issued Tuesday, with military spokesman Rear Adm. Daniel Hagari saying the cause of the fire was still under investigation but that the Israeli munitions used — targeting what the army said was a position with two senior Hamas militants — were too small to be the source.

The strike or the subsequent fire could also have ignited fuel, cooking gas canisters or other materials in the camp. The blaze killed 45 Palestinians, according to Gaza health officials’ count. Israeli Prime Minister Benjamin Netanyahu said the fire was the result of a “tragic mishap.”

Israel's assault on Rafah, launched May 6, spurred more than 1 million people to flee the city, the U.N. agency helping Palestinian refugees said Tuesday. Most were already displaced multiple times in the nearly eight-month war between Israel and Hamas. Families are now scattered across makeshift tent camps and other war-ravaged areas.

The strikes over the past few days have hit areas west of Rafah, where the military had not ordered civilians to evacuate. Israeli ground troops and tanks have been operating in eastern Rafah, in central parts of the city, and along the Gaza-Egypt border.

Shelling late Monday and early Tuesday hit Rafah’s western Tel al-Sultan district, killing at least 16 people, the Palestinian Civil Defense and the Palestinian Red Crescent said. Seven of the dead were in tents next to a U.N. facility about about 200 meters (yards) from the site of Sunday's fire.

“It was a night of horror,” said Abdel-Rahman Abu Ismail, a Palestinian from Gaza City who has been sheltering in Tel al-Sultan since December. He said he heard “constant sounds” of explosions overnight and into Tuesday, with fighter jets and drones flying above.

He said it reminded him of the Israeli invasion of his neighborhood of Shijaiyah in Gaza City, where Israel launched a heavy bombing campaign before sending in ground forces in late 2023. “We saw this before,” he said.

The United States and other allies of Israel have warned against a full-fledged offensive in the city, with the Biden administration saying this would cross a “red line” and refusing to provide offensive arms for such an undertaking. On Tuesday, U.S. State Department spokesman Matthew Miller gave no indication the administration sees Israel as crossing any of the red lines for Rafah, saying the offensive is still on a “far different” scale than assaults on other population centers in Gaza.

The International Court of Justice has ordered Israel to halt its Rafah offensive as part of South Africa's case accusing Israel of committing genocide against the Palestinians in Gaza.

On Tuesday afternoon, an Israeli drone strike hit tents near a field hospital by the Mediterranean coast west of Rafah, killing at least 21 people, including 13 women, Gaza's Health Ministry said.

A witness, Ahmed Nassar, said his four cousins and some of their husbands and children were killed in the strike and a number of tents were destroyed or damaged. Most of those living there had fled from the same neighborhood in Gaza City earlier in the war.

“They have nothing to do with anything,” he said.

Netanyahu has vowed to press ahead in Rafah, saying Israeli forces must enter the city to dismantle Hamas and return hostages taken in the Oct. 7 attack that triggered the war.

In its investigation of Sunday’s deadly strike and fire, the Israeli military released satellite photos of what it said was a Hamas rocket launch position about 40 meters (yards) from an area of sheds that was targeted. In the photo, the alleged launcher itself did not appear to have been struck.

He said Israeli warplanes used the smallest bombs possible — two munitions with 17-kilogram warheads. “Our munition alone could not have ignited a fire of this size,” he said.

Hagari said that the fire was “a devastating incident which we did not expect” and ignited due to “unforeseen circumstances.”

Still, the strikes have triggered a flight of people from areas west of Rafah. Sayed al-Masri, a Rafah resident, said many families were heading to the crowded Muwasi area or to Khan Younis, a southern city that suffered heavy damage during months of fighting.

“The situation is worsening” in Rafah, al-Masri said.

Gaza’s Health Ministry said two medical facilities in Tel al-Sultan are out of service because of intense bombing nearby. Medical Aid for Palestinians, a charity operating throughout the territory, said the Tel al-Sultan medical center and the Indonesian Field Hospital were under lockdown with medics, patients and displaced people trapped inside.

Most of Gaza’s hospitals are no longer functioning. Rafah’s Kuwait Hospital shut down Monday after a strike near its entrance killed two health workers.

A spokesperson for the World Health Organization said the casualties from Sunday’s strike and fire “absolutely overwhelmed” field hospitals in the area, which were already running short on supplies to treat severe burns.

“That requires intensive care, that requires electricity, that requires high-level medical services,” Dr. Margaret Harris told reporters in Geneva. “Increasingly, we are struggling to even have the high-level skilled doctors and nurses because they’ve been displaced.”

The war began when Hamas and other militants burst into southern Israel in a surprise attack on Oct. 7, killing some 1,200 civilians and abducting around 250. More than 100 were released during a weeklong cease-fire in November in exchange for Palestinians imprisoned by Israel.

Israel responded to the attack with a massive air, land and sea offensive that has killed at least 36,096 Palestinians, according to Gaza’s Health Ministry, which does not distinguish between fighters and civilians in its count. Around 80% of Gaza’s population of 2.3 million has been displaced and U.N. officials say parts of the territory are experiencing famine.

The fighting in Rafah has made it nearly impossible for humanitarian groups to import and distribute aid to southern Gaza.

The Israeli military says it has allowed hundreds of trucks to enter through the nearby Kerem Shalom crossing since the start of its operation, but aid groups say it’s extremely difficult to access that aid on the Gaza side because of the fighting.

The U.N. says it has only been able to collect aid from around 170 trucks over the past three weeks via Kerem Shalom. Smaller amounts of aid are entering through two crossings in the north and by sea through a U.S.-built floating pier, but it’s nowhere near the 600 trucks a day that aid groups say are needed.