A car-alarm siren triggered early Thursday led police to charge three teenagers with breaking into cars here and in Bridgeport.

A Riverside Drive resident called police about 5:30 a.m. Thursday after the alarm in his pickup truck began sounding. When he went to check on the truck, he found it had been broken into. One of the officers responding to the call spotted two teens on bikes nearby on Turney Road. In the pocket of one of the teens was a flashlight that was still lighted.

An open butterfly knife was found on the ground near Brian Rodrigues, 18, police said. The 17-year-old accompanying him -- who had the flashlight -- had a backpack filled with more than $500 in stolen items, including credit cards, marijuana and several bottles of beer, according to the report.

Meanwhile, officers received a call from another Riverside Drive resident who said there was a third teen in his backyard, and a high-end racing bike propped up against his house. That teen, also 17, was also taken into custody, and a second backpack was located in nearby bushes. He had $109 in cash in his sock, and there were headphones, a cell phone, chargers, an iPad cover and garage door opener in that backpack, police said.

One of the credit cards was traced to a resident of Lake Avenue in Bridgeport, while others were traced to a resident of Piersall Place in Bridgeport. The Piersall Place residents refurbish bikes for charity, and had about 30 bikes on their property. Police are investigating whether the bikes the three were using were taken from that house.

Police also are looking into whether the trio is connected to some car break-ins the previous night on Blaine Street and another on Lind Street.

Rodrigues, of Whetstone Hill Court, was charged with possession of a dangerous weapon, third-degree burglary and conspiracy to commit third-degree burglary. He was released after posting a $1,000 bond and is scheduled to appear Aug. 29 in Bridgeport Superior Court.

The first juvenile, who was found with Rodrigues, was charged with four counts of third-degree burglary, four counts of conspiracy to commit third-degree burglary, possession of burglary tools, larceny by possession, possession of marijuana, possession of intent to sell, and possession of alcohol by a minor. Police said he has no known address and they were seeking his remand to a juvenile detention facility.

The second 17-year-old, who lives in Fairfield, was charged with conspiracy to commit third-degree burglary and simple trespass. He was released to his parents' custody.