An apartment building and coach house were evacuated after a sinkhole formed on a cement patio between the West Town structures early Friday.

Someone flagged down police in the 1400 block of West Chicago Avenue about 1 a.m. after the 20-foot long by 20-foot wide hole opened, said Chicago Police Officer Janel Sedevic, a department spokeswoman. The hole is about 10 feet deep, she said.

Emergency crews evacuated the apartment and coach house behind it but no one was hurt, Fire Media Affairs Chief Larry Langford said.

The hole formed in a concrete area between the coach house and the four-story building, which includes Butterfly Sushi Bar on the first floor and three floors of apartment units above, according to a man at the scene who identified himself only as an employee of the building manager.

The owner of the building decided to vacate all eight units in the apartment and coach house, and would help find tenants other places to stay, according to Amy Simon, spokeswoman for the Chicago Department of Buildings.

A passageway between the basement levels of the coach house and the apartment that had been sealed years ago by a previous owner collapsed under the concrete, possibly due to heavy rains earlier in the week, said the building worker. Tenants kept patio furniture in the area of the collapse; it was also the area that housed the units’ air conditioners, he said. Restaurant workers used the path to take out trash.

“The rain was probably the straw that broke the camel’s back,” he said as he directed crews to install boards to bridge the sinkhole.

Authorities didn’t know the cause of the sinkhole later Friday; city inspectors were evaluating the damage.

The restaurant was closed Sunday as a result of the sinkhole, according to a staffer who answered the phone there.

Alexandra Shoemaker, 24, who lives on the second floor of the apartment, said she came home early Friday to numerous police and fire crews around the building, who told her the building was safe to stay in. She said she decided to stay at her boyfriend’s apartment after she saw the extent of damage this morning.

“I looked down and the back patio was gone,” Shoemaker said.

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