A bomb exploded on Tuesday at the main power station of Brazil's top port of Santos but the port suffered no interruption in power, said the port authority Codesp.
"The main power station collects energy from the regional grid and powers nearly all the port's operations. Energy supply was uninterrupted and police are investigating the nature of the bomb," said a Codesp Port Authority official.
Santos, Latin America's largest port, has been in the midst of a dockworkers' strike since last Tuesday. A local labor court declared the strike an act of civil disobedience on Friday and ordered the workers back on the job.
A high-tension power line tower that brings electricity to ship terminals at Santos was sabotaged early Monday morning, at which time a portion of the port shut down until 6 p.m. local time when the tower was fixed - the police said they had no suspects.
The dockworkers' union refused to end its protests and has been fined $23,000 daily by the labor court. Protesters have continued to rough up strike breakers and cause havoc for companies trying to carry on work without union workers.
An officer of the Santos police said more than 30 demonstrators were arrested on Monday when riot squads and dockworkers faced off in a shower of rocks, rubber bullets and tear gas. Union dissidents retreated and broke up following the riot police charge.
The port spokeswoman said ship movement was normalizing at the port with the help of riot police squads to protect some of the grain companies who have been operating without union workers to load and unload ships.