WASHINGTON (Reuters) - Police evacuated the office of anti-tax lobbyist Grover Norquist in Washington on Monday after a caller phoned his office with a bomb threat, authorities said.

No explosives were found and police said they had no information on a possible motive.

Norquist and his lobby group, Americans for Tax Reform, have played an outspoken role in the rancorous debate about whether to raise the $14.3 trillion U.S. debt ceiling.

Officer Anthony Clay said city police sealed off a one-block section of downtown Washington shortly after 9 a.m. EDT, while officers with bomb-sniffing dogs searched the office of Americans for Tax Reform for explosives.

They sounded the all-clear about two hours later, allowing the organization's staff to return to work.

Americans for Tax Reform had no immediate comment on the incident.

(Reporting by David Morgan; Editing by Jackie Frank)