STERLING HEIGHTS, Mich. (AP) -- Contractors found about a dozen pieces of human flesh and other body parts Wednesday while they were clearing debris in a sewer pipe 50 feet below a busy suburban Detroit roadway.

Workers stumbled upon the parts about 8:30 a.m. while beginning their daily work in the 9-foot, 6-inch-wide pipe in Sterling Heights.

"It's not like there were arms or legs, it was small pieces," said Sterling Heights Police Lt. Luke Riley. "One of the pieces has what appears to be part of a tattoo."

Investigators don't believe the parts had been in the sewer too long, Riley said.

The Macomb County medical examiner's office was examining the pieces. Authorities also were checking on missing person's reports.

The parts are believed to have washed into the work area from one of two large lines flowing into the sewer from the north and west. The 21-mile-long line continues south from Macomb County into Detroit where it goes through a pumping plant before dumping into the Detroit River.

Each morning workers close doors shutting the flow of water and debris from the two lines so they can do grouting and other repairs in the sewer, said Gene Schabath, Macomb County's deputy public works commissioner.

As the water flowed slowly through the gravity-fed sewer, debris piled up on their work platform.

"They were removing all the debris that accumulated ... under the debris were these body parts of various sizes," Schabath said.

It would be difficult to determine how the parts were put into the system, he added.

"We have all these lateral lines that tie into it," Schabath said. "There are over 100 manholes where parts could have been dropped into."

To prevent a possible backup into homes, the two lines were reopened Wednesday after the body parts were removed and sections along the pipe checked for other parts or evidence.

Other sewer grates further along the line also were being checked, Schabath said.

The parts were not in the section of sewer when the contractors finished their work Tuesday afternoon, he added.

The discovery comes one month after torsos and other body parts of an Allen Park couple were found in the Detroit River and a canal leading into the waterway in Detroit. Later that day, an angler spotted what later were identified as legs, a circular saw and a suitcase submerged along a seawall near where the torsos were found floating.

A man who had been a guest of the couple's home just west of Detroit has been charged with murder in that case.