Police here are trying to determine if the weekend drowning of a Vietnamese man who was pushed into the water of a Lake Michigan harbor was a hate crime, saying the man was the third fisherman who appeared to be Asian to be targeted.

"Based on the pattern, there is a possibility that it could be a hate crime," Chicago police spokeswoman Monique Bond said Tuesday of the drowning death of Du Doan, 62. "It's a very strong possibility."

Bond said three people who she described as "persons of interest" were being interviewed by detectives Tuesday but no charges had been filed.

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Police said Doan was fishing by himself early Saturday off the sidewalk of Montrose Harbor on the city's North Side when he was pushed into the water.

"Five individuals dressed in black gothic clothing walked past him, and one of the individuals breaks away from this group ... and gives him a shove in the back and knocks him into the water," Lt. Anthony Riccio said.

Doan did not know how to swim and quickly drowned as several people tried to rescue him with nets and poles.

Police said a short time before Doan was shoved into the water, another fisherman of Asian descent was confronted by the same group. The other man, though, did not back away, and the group spit at his feet and left him alone, police said.

A few weeks earlier, a man with Asian features was pushed into the water by a group that fits the description of the one that approached Doan and the other fisherman Saturday.

The man swam to shore, police said. He only reported the incident after hearing about Doan's death.

Riccio noted police had not officially classified Doan's death as a hate crime, saying it might be a "really stupid practical joke ..."

But police were concerned enough about the incidents to distribute fliers describing the suspects and warning fisherman to be careful, and for people using the lakefront early in the morning or late in the evening not to travel alone.