WASHINGTON (AP) — Police Chief Cathy Lanier says the increased law enforcement presence on Washington’s streets will continue until the threat has decreased.

Counterterrorism officials have been chasing a tip that al-Qaida may have sent three men to the United States to detonate a car bomb, authorities have said. Lanier said in an e-mail on Monday that the Metropolitan Police Department is paying close attention to the threat.

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She says the increased police presence will remain until she is comfortable that the threat has decreased. Lanier last week said her officers would be working 12-hour shifts indefinitely. The chief says she’ll do everything possible to keep residents and visitors to the District of Columbia safe.

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The chief said in a separate directive that scheduled days-off for Tuesday and Wednesday would be canceled.

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