The U.S. Senate voted to advance a four-year extension of provisions of the USA Patriot Act allowing law enforcement to track suspected terrorists with roving wiretaps.

The Senate voted 79-18 to move toward a final vote on the provisions, now scheduled to expire at midnight. They would be extended until June 1, 2015.

The bill’s roving-wiretap section allows federal agents to obtain a single warrant to monitor phone calls of suspects using a series of mobile phones.

Other powers in the legislation let authorities obtain business and library records, and target so-called “lone wolf” suspects who aren’t affiliated with any terrorist group.

The Patriot Act was passed after the Sept. 11 attacks, and many of its provisions are permanent law. Some of its surveillance powers have been opposed by some lawmakers and outside groups, including civil liberties activists.

Both chambers approved a three-month extension in February.