Five protesters were this week arrested during a demonstration against the construction of an animal research laboratory at Oxford University.

The arrests came after protest group SPEAK warned that it would continue to target the contractor working on the project even after its contract had ended. SPEAK believes it knows the identity of the company involved, and is this week writing to demand a statement clarifying the company's position. The contractor concerned has said claims of its involvement are "100% untrue".

Robert Cogswell, spokesperson for SPEAK, warned: "The animal rights movement has a long memory. Whichever company is working on the project should not be thinking that it can leave at the end of the contract and simply walk away. We will be thinking outside the box and finding imaginative ways to put pressure on people."

Work on the research facility restarted in November. Montpellier, the original contractor, abandoned the project in July 2004 after pressure from extremists.

Workers on the site are wearing masks that conceal their identity from the campaigners. Workers are escorted to the site each day in unmarked cars, overseen by a police helicopter.