The reforms, which were approved earlier by the Senate, are backed by President Felipe Calderon and come as Mexico is shaken by organized-crime violence that has claimed almost 5,400 lives so far this year, more than double the death toll from the same period of 2007.

They allow taped conversations to be used in court if submitted as evidence by one of the parties in the conversation, and let police request search warrants by e-mail or by telephone calls to judges rather than exclusively in writing, according to a Congressional statement.

The changes also permit undercover agents.

Many Mexican detectives currently operate in plain clothes, but the new measure would let them keep their identities secret in legal proceedings and be identified by a numerical code known only to superiors.

Drug gangs have increasingly targeted police officials for assassination in recent years.

The reforms include some safeguards meant to prevent police from abusing their powers, including one requiring that officers quickly register all detentions. Under current law, they have up to two days to present a suspect before a judge.

In the past, some police have been accused of using that period to threaten, pressure or torture suspects into confessing.

The bill also tightens the definition of catching a suspect "in the act," to mean just a few moments from the commission of a crime. Previously, police could detain suspects hours or even days after a crime and claim they had been caught in the act.

Also Tuesday, the Senate voted to create a registry of cell phone owners to combat kidnappings and extortions in which gangs often use untraceable mobile phones to make ransom demands.

Telecoms would be required to ask purchasers of cell phones or phone memory chips for their names, addresses and fingerprints, and to turn that information over to investigators if requested.

At present, unregulated vendors sell phones and chips for cash from streetside stands. It is unclear how such vendors would be made to comply with the new law.

The Senate also approved a bill previously passed by the lower house to standardize police training, vetting and operational procedures.

The law would create a national security council headed by the president and the governors of Mexico's 31 states to improve coordination among a disparate array of state, local and federal police.

The bill will return to the lower house for final approval after senators detected errors in its wording.