Malei Jones was swimming in a basin near the Nine Mile Run trail before he nearly drowned there, city police said. And he swam despite a nearby sign posted by city officials discouraging the activity.

City and park officials said the water is heavily polluted. Nonetheless, Malei started to swim Tuesday and before he went underwater in a 10-foot-deep area for about 10 minutes.

Police are still investigating the incident. Police Cmdr. Thomas Stangrecki said Malei was in critical condition at UPMC Children's Hospital.

A hospital spokesman could not confirm Wednesday afternoon. The boy's parents requested no information be released about their son.

The parks department sign was the only warning visible near the Nine Mile Run trail. It was located at the end of the culvert leading into a water basin.

Parks and Recreation Director Duane Ashley did not respond to a request for comment left at his office Wednesday.

In an interview with the Post-Gazette, Cmdr. Stangrecki revealed new details about the incident. Malei was playing with two friends, ages 11 and 14, and his 7-year-old sister, Cmdr. Stangrecki said.

The two friends entered the basin first, while the sister watched. Malei joined the two, but soon started to struggle and yelled for help.

Police said the water level was elevated due to last week's storm. Cmdr. Stangrecki said he is not sure whether the two friends could find Malei underwater as he was submerged.

The polluted water has abnormally high levels of E. coli and other bacteria, due to the sewage that has leaked into the water, said Brenda Smith, executive director of the Nine Mile Watershed Association.

"It is definitely not safe to swim," Ms. Smith said of the waters.

From 2002 to 2006, the stream underwent a renewal as members of the Army Corps of Engineers took measures to slow down the stream current and planted natural species of plants in the area.

The restoration helped to encourage more people to walk by the stream and to participate in events near the water.

Ms. Smith said many people frequently walk or bike through the nearby trails. Because of this, she said it is difficult to prevent people from entering the dirty stream.

"It's a public park. There is no way from protecting people at all times of all the hazards," Ms. Smith said.