BATH — A member of Bath Iron Works’ largest union was knocked to the ground by a slow-moving vehicle Wednesday evening while picketing.

According to Bath Deputy Police chief Andy Booth, the vehicle was attempting to exit the shipyard through the south gate on Washington Street around 10 p.m. Wednesday when picketers holding signs surrounded the car. The car edged forward, striking one picketer, who was knocked down. No one was injured.

The incident is under investigation, and police declined to release the identities of those involved.

Members of Local S6, which represents 4,300 of BIW’s 6,700 employees, voted to strike last weekend after contract negotiations floundered.

Booth said police weren’t stationed at the south gate and union supervisors weren’t present, but a four-second video of the confrontation surfaced on Facebook Thursday morning.

“It doesn’t look intentional, but the district attorney is investigating,” said Booth. “I don’t expect criminal charges. The picketers violated their own picketing rules by harassing the vehicle.”

On Sunday, the day before the strike began, union officials issued a list of 24 rules members must obey while on the picket line.

“Certain conduct … works against our goal of a positive strike, can have serious financial consequences and will not be tolerated,” union officials wrote to members.

One rule prohibits picketers from obstructing entrances or exits of the premises, and states: “Do not interfere with, or swarm, persons or vehicles entering or leaving the job.”

The union’s rules also prohibit picketers from photographing or recording people entering or leaving the shipyard.

Booth said there have been some close calls when protesters get too close to cars trying to enter or leave the shipyard since the strike began early Monday morning.

“I’m meeting with union leadership daily to address these concerns,” he said.

Both state and local police try to control the groups of union members who gather in front of the shipyard’s gates, but Booth said it’s difficult for officers because “you get a new group of picketers every four hours.”

Local S6 union members must picket for at least four hours to receive a $150 stipend from the union.

Booth said the strike has been otherwise peaceful. Some locals have filed noise complaints, and police issued a ticket after someone did a burnout on Washington Street in front of picketers. Booth said officers are issuing warnings to people making excessive noise with their vehicles, such as honking their horns continuously from the south entrance to the north entrance of the shipyard.

“We’re fine if people want to honk in solidarity, play music and shout,” Booth said Tuesday. “We’re not trying to stop picketers from expressing their first amendment rights. … If the noise is reasonable, we don’t have a problem with it, but once it gets unreasonable, we have a duty to uphold the state law for the rest of the citizens of Bath.”

Both BIW and Local S6 leadership did not return requests for comment Thursday.