Sunrise on the Bloomingdale Trail View Full Caption DNAinfo/Alisa Hauser

HUMBOLDT PARK — Armed thieves on the west end of the elevated Bloomingdale Trail have knocked cyclists off their bikes to beat and rob them twice this weekend, and Chicago police are warning those who use the 606 park system to watch out.

Three incidents this month on the trail, a former elevated railroad line, were the subject of a police alert Sunday evening.

The robberies happened July 2 and this weekend.

Police said the men knocked the victims from their bikes as they rode on the 606.

"In the first two incidents, the victims suffered injuries when they fell off their bikes. In the latest incident, the offenders were armed with a small black handgun, and the offenders beat the

victim and demanded his belongings," police said in a news release.

The attacks happened:

• July 2, 2017 at 1:15 a.m. at 3510 W. Bloomingdale Ave.

• July 22, 2017 at 5:29 p.m. at 3300 W. Bloomingdale Ave.

• July 23, 2017 at 4:30 a.m. at 1850 N. Ridgeway Ave.

The robbers were described as black men, one wearing a black "doo-rag", brown long-sleeved shirt and black shorts. Another had short hair, and wore a white T-shirt and jeans.

During two of the incidents, the trail was closed.

The trail and park system is open from 6 a.m. to 11 p.m. daily.

A similar incident where a cyclist was pulled off a bike and robbed by several thieves was reported in February 2016.

RELATED: Is The 606 legally open to late-night biking? Police Say No; Cyclists Say Yes.

Police said trail visitors should:

• Be aware of surroundings.

• Pay special attention to suspicious people.

• Be conscious of suspicious activity or people.

• Call 911 immediately and provide a detailed description of offender(s), including any vehicle description and license plate information.

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