A 56-year-old homeless man was killed early Wednesday in Portland when he was crushed by a front-end loader driven by an employee of the city’s Public Services Department.

The man, whose identity has not been released by police, was apparently sleeping behind the rear tires of the large piece of equipment as it was parked inside the city’s salt shed at 83 Hanover St.

Wayman Estes, 55, of South Portland, who is a maintenance worker for the department’s night crew, started up the machinery at 2:30 a.m. and backed it over the sleeping victim.

Estes is part of a night crew that conducts street sweeping in Portland and was about to use the loader to transfer debris collected by the sweepers into a dump truck for disposal, said city spokeswoman Nicole Clegg. The loader was parked in the open-ended shelter that covers a city salt pile.

The department is conducting an internal review of the incident while the police conduct their own investigation, but it is too early to tell whether the incident will lead to any policy changes at the department.

“It’s a very tragic accident,” said Clegg, who said the incident was traumatic for the entire crew, including Estes. “We’ve never had to deal with a situation like this before.”

Police are withholding the man’s identity until his family can be located and notified, said police Capt. Vern Malloch.

Police believe the victim has been a longtime resident of the city. Officers met with staff of the city’s homeless shelters and the staff at Preble Street, a nonprofit group providing assistance and advocacy for the homeless, to learn more about the man’s background.

The Public Services facility is in the same neighborhood as Preble Street’s resource center and the Oxford Street Shelter, and homeless people occasionally seek shelter in that area in the doorways of businesses or in unlocked vehicles.

City officials and police said they were unaware that people might seek shelter in the salt shed, but the area is not fenced off.

Police ask that anyone who witnessed the accident contact the department’s traffic division at 874-8532.

Clegg said she hopes the accident will at least encourage other people to forgo the vulnerability of sleeping outside in favor of one of the city’s shelters.

The city operates shelters for adults, for families, for teenagers and for people who are under the influence of alcohol.

The Oxford Street Shelter for Men’s Support Services Team, a group of city housing counselors, is available between 1 p.m. and 8 a.m. to help homeless individuals and families, Clegg said. The assistance is available by calling 761-2072.

People also can call 211 to find out more about city services for the homeless.