The union is rolling out the strike and it's impacting more companies. That list already includes Cisco, Intel, Yahoo, Oracle, HP and Applied Materials.
Tension on the picket lines is escalating. On Tuesday afternoon, striking janitors blocked two trucks trying to get replacement workers onto Cisco Systems property.
San Jose police officers stood by, ready to make arrests if necessary. They waited for a top union official who came in and convinced the crowd to back down.
After more than an hour long stand-off the trucks rolled onto Cisco property.
"Our strikers won't get arrested, at least for now and the strike continues. We made as much of a point as we wanted to we want to make at this point," said SEUI Local 1877 president Mike Garcia.
There was another incident at Yahoo, where strikers say an aggressive driver upset with the picketers left skid marks. A janitor was taken to the hospital but other picketers couldn't tell us exactly how she was injured. They say she may have been hot or may have fallen.
The woman apparently hurt her back and hip and police are investigating. The janitor's strike is hitting more companies every day and is now being honored by more than a hundred unions.
"All of the unions that belong to our labor company, teamsters who deliver trash, folks who do construction work , people who do electrical work, people who do communications and cable wok, non of these folks will cross the picket line," said Phaedra Ellis-Lamkins from the South Bay Labor Council.
The union representing 6,000 janitors is putting pressure directly on Silicon Valley's high tech companies to get involved. The janitors actually work for 16 cleaning companies.
In a statement, an Intel spokesperson said: "we understand the issues. We are a third party. We are not negotiating."
The union says high tech companies with big profits need to take responsibility because workers like Maria Lopez can not support her four children on $11an hour.
"Cisco is good. My company is good only I need more salary and insurance," said Lopez.
The strike will now spread to commercial buildings in downtown Oakland, and on Thursday, the janitors will stage a one-day walkout at Stanford University.