(CNN) They're in their early 20s. They communicate and coordinate operations through a Telegram social media group. And they're helping to clean up Venice during its devastating floods.

Hundreds of people descended on the flooded streets of the historic Italian city on Thursday to provide help to Venetians in difficulty -- draining houses or stores, moving household goods, collecting waste and sending it for recycling. Even more are on the ground Friday, after a high tide reached 5 feet, according to the organizers.

The volunteers are part of Venice Calls, an organization that has been active for more than a year, its spokesman, 25-year-old Piero Risica, told CNN.

Volunteers clean up flooded Venice.

"When we saw the historic flooding on Tuesday night, we immediately started to gather volunteers to help the city. The first day we were 200 in the Telegram group and on the ground. Yesterday 550, and today more than 1,700," Risica said.

While the Venice Calls core group is made of 35 people, all students between 18 and 25, Risica said hundreds of people from all age groups and from all over Italy responded to the call for help.

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