As drug smugglers carried hundreds of pounds of marijuana through a tunnel from Canada to the U.S. last month, federal officials heard every word and watched nearly every movement with state-of-the-art surveillance.

Investigators were able to surreptitiously install video and audio bugging devices in the tunnel after receiving a judge's approval to search the passage under a controversial provision of the USA Patriot Act.

By obtaining a so-called "sneak-and-peek" warrant, law-enforcement officials were able to enter the tunnel, and bug it, without immediately telling the suspects a warrant had been issued. Regular search warrants require that the subject of a search be notified immediately after it has been conducted.

As Congress prepares to reauthorize some parts of the terrorism-fighting Patriot Act this summer, some legislators and civil-rights groups say that power is too broad and want to regulate the ways police can conduct searches. The Senate Judiciary Committee recently introduced a bill that would greatly limit how "sneak-and-peek" actions are conducted.

"I think that the power that the government has under the Patriot Act ... is clearly contrary to the notion underlying the Fourth Amendment," said former U.S. Rep. Bob Barr, a Republican from Georgia who leads the Patriot Act reform organization Patriots to Restore Checks and Balances.

Sneak-and-peek "is being used in cases that have nothing whatsoever to do with terrorism," Barr said. When police want to search a suspect's property, a judge has to determine there is probable cause before issuing a warrant. After police search the property, they are normally required to leave a notice with explanations of the areas searched and items removed, if any.

Under a sneak-and-peek warrant, also known as a delayed-notice search warrant, a judge authorizes police to search a suspect's property without leaving any trace they were there. Whalley said investigators arrange the timeline of the delay with a judge and most often notify suspects within 30 days.

Doug Whalley, an assistant U.S. attorney in Seattle, said the Patriot Act codified already-existing law, making it difficult to challenge the use of sneak-and-peek warrants in court. Rulings before the act were made on a case-by-case basis, Whalley said, and appeals courts could have ruled the warrants were improperly issued.

But Lisa Graves, senior counsel for legislative strategy for the American Civil Liberties Union, said that under these warrants, police routinely don't tell suspects they have searched their homes until months later. Graves also said the new Patriot Act provisions have been an attempt to give law enforcement a blanket ability to conduct secret searches without being held accountable.

"The Justice Department decided to create a statutory right across the board," Graves said, "to try and create a national right of law enforcement to create secret searches of businesses and homes, secret seizures of evidence."

"Federal prosecutors don't eagerly use these methods of surveillance," countered Whalley. "The process is very labor intensive. If you watch TV, they get a search warrant within 10 minutes. Something like this, where you want to go in and not announce your presence — if we're lucky, the turnaround is two days, and that's fast."

When authorities announced the discovery of the tunnel in mid-July, federal officials said their concern was not only drug smuggling but the possibility it could be used to transport terrorists or smuggle weapons.

But civil-rights advocates say law-enforcement agencies are abusing their power.

"The tunnel has nothing to do with the war on terrorism. ... There's absolutely no reason why the authorities couldn't have availed themselves of the normal ways possible," said Bob Mahler, a Seattle criminal-defense attorney. "They just didn't feel the need to use the normal, constitutionally mandated processes because they had this new tool that was given to them."

The section of the act containing the sneak-and-peek provisions is not up for congressional reauthorization this year, but advocates still want it amended during this series of revisions.

U.S. Sen. Patrick Leahy, D-Vt., ranking member of the Senate Judiciary Committee, announced last month that the committee unanimously approved a bill to reform parts of the Patriot Act, including more regulation of police searches and sneak and peek.

Under the bill, the government would have to notify the target of a sneak-and-peek warrant within seven days of a search. Week-by-week extensions could be requested, bringing additional judicial oversight.

Sen. Maria Cantwell, D-Wash., co-sponsored a similar but further-reaching bill, the Security and Freedom Ensured, or SAFE, Act.

If passed, it would require added judicial oversight, much like Leahy's bill, and also would limit the grounds for delayed-notice search warrants. They would be allowed in cases when authorities feared there could be destruction of evidence, risk of injury, intimidation of witnesses or that suspects would flee, among other circumstances.