Officials are investigating after a retaining wall dislodged and collapsed Sunday in the backyard of a five-story apartment building in the Bronx, cracking the ground and sending debris into the building.

The collapse happened around 11:50 a.m. behind 3138 Bailey Ave. near Summit Place in Kingsbridge.

The city fire department said the wall — which was about 30 feet wide and 60 feet long — collapse ejected debris into the backyard and some basement windows, and damaged fire escapes.

Photos from the fire department show the collapse cracked open the ground near the base of a building.

The FDNY said no injuries have been reported at this time, and no one has been reported missing.

To be sure, however, first responders were searching 3138 Bailey Ave., and the building behind it, Sunday afternoon to make sure no one was missing.

Due to the sheer volume of debris, first responders are also searching the collapse scene with rescue dogs and thermal scanners to make sure no one is under the rubble. Fire department officials said it is a process that will take all night.

Residents said three construction workers were behind the building at some point Sunday. The FDNY said it's not clear what they were doing there but they were all accounted for and were unhurt.

The city buildings department, which is investigating the property, hasn't confirmed why the wall collapsed.

The fire department said it's not clear if the wall was part of the 3138 Bailey Ave. building or the building behind it. A fence was between the two.

Several apartments in both buildings have been evacuated because the fire escapes are no longer accessible. Those residents were being sheltered on city buses as of Sunday afternoon.

Some apartments in the buildings that use fire escapes may be evacuated later on, the FDNY said.

Photo above via the FDNY on Twitter.