The Cambridge City Council is taking a wait-and-see approach towards a Cambridge biotechnology company construction project after an impassioned meeting Monday afternoon.

The council agreed to allow City Manager Robert Healy to investigate the numerous--and often conflicting--claims made at the meeting by James Mullin, vice president of Biogen, Inc. and representatives of Local 40, the carpenter's union.

At the special meeting, Local 40 representatives asked the council to repeal a 47 percent tax break awarded to Biogen last September. Biogen received the subsidy for the construction of a $35 million office, lab and manufacturing facility in Kendall Square.

The council had given Biogen the tax break under Chapter 121A, a clause allowing the city to charge a reduced tax rate on a parcel of land to attractcompanies to build.

Under the 121A arrangement, Biogen saves about$287,000 per year over the 15-year life of thedeal.

Mark Ehrlich, the Local 40 Manager, said thathe and the union originally opposed the 121A deal.He said he changed his mind when he, speaking forthe union, reached a verbal agreement withMarshall Contractors that only union labor wouldbe hired.

Biogen had hired Marshall to award subcontractsfor the project.

With Marshall's assurance, Ehrlich dropped hisopposition and the council unanimously approvedthe 121A tax status on September 13--without awritten agreement.

Ehrlich said he tried for months to finalizethe deal with Marshall, but said the agreement wasrepeatedly delayed for logistical reasons.

In March, Ehrlich said, he closed the deal withMarshal and sent the company a written contract,fully expecting a signature. But Marshall told himthat there would be no deal, and that non-unionworkers might be hired.

There were no representatives present fromMarshall, which is based in Rhode Island.

Ehrlich said he believes Biogen is to blame forthe lack of agreement and wants to repeal the taxbreak.

"We in effect in the city are subsidizing acompany which is subsidizing an undergroundeconomy," Ehrlich said, citing Marshall's allegedhistory of employing subcontractors barred fromfederal projects for unfair labor practices.

Defending Biogen, Mullin said that the contractdispute was solely between Marshall and Local 40and had nothing to do with his company.

He said several times that Biogen did not havea part of any of the meetings between Marshall andthe union.

"We believe this is a private disagreement inwhich neither Biogen nor the city council isrightfully involved," Mullin said.