Despite an early morning earthquake that rumbled nearby, federal officials insisted Friday that the site of a proposed national nuclear waste repository in the Nevada desert is safe.

No damage or injuries were reported after the magnitude 4.4 temblor struck at 5:40 a.m. The earthquake was centered about 12 miles southeast of the Yucca Mountain site and 75 miles northwest of Las Vegas, according to the U.S. Geological Survey in Golden, Colo.

The earthquake went unnoticed on the Las Vegas Strip but was felt in Pahrump, 40 miles to the southeast.

It also reverberated in Washington, where the Senate is due by July 26 to vote on whether to entomb highly radioactive waste at Yucca Mountain.

"The earthquake is a wake-up call for the U.S. Senate," said Rep. Shelley Berkley, D-Nev., who raised the specter of radioactivity contaminating groundwater if an earthquake were to strike an active repository.

The House has already voted to support President Bush's selection of Yucca Mountain as a storage site for the nation's high-level radioactive waste.

"Today, we saw more proof that the proposed Yucca Mountain nuclear dump site is not safe," said Sen. Harry Reid, D-Nev., who has so far tried unsuccessfully to drum up votes to block the project in the Senate.

The Energy Department plans to bury 77,000 tons of spent commercial, industrial and military nuclear waste in a grid of underground tunnels beneath the ancient volcanic ridge. The site would remain radioactive for more than 10,000 years.

Allen Benson, a department spokesman, released a statement calling the area "a known and studied geologic zone" that project scientists have monitored for 24 years.

He said a magnitude 5.6 earthquake in 1992 in the same area — near Little Skull Mountain in the Nevada Test Site — didn't dislodge boulders at Yucca Mountain.

"Scientific studies show that an underground repository at Yucca Mountain would perform safely in accordance with regulatory standards, including during an earthquake," he said.

David von Seggern, a seismologist at the Nevada Seismological Laboratory at the University of Nevada, Reno, said Friday's earthquake was no surprise.

"Earthquakes have happened and will continue to happen in this area," he said.

He said Yucca Mountain is in a 6-mile zone in which scientists found no documented evidence of an earthquake greater than magnitude 3 since the 1800s.

A quake of magnitude 4.4 or even 6.4 would not damage a well-designed nuclear repository, von Seggern said.

Opponents seized on the quake as a reason to reject Yucca Mountain.

"If you're out looking for sites, three things you want to avoid are earthquakes, the potential for volcanoes and contamination of a pristine and valuable aquifer," said Judy Treichel, an executive director of the Las Vegas-based Nuclear Waste Task Force.