A loud noise rattled more than 100 people attending a candlelight vigil Saturday outside the headquarters of Rep. Gabrielle Giffords, where authorities investigated a suspicious package that turned out to be non-explosive.

Police department spokesman Lt. Fabian Pacheco says an officer checking Giffords' office in Tucson had found a "strange" item that he said resembled a coffee can and had writing on it. Pacheco would not disclose what the writing said.

A bomb squad worked for a couple hours, using X-ray equipment, to try to figure out what the package was before the loud noise was heard. The noise was caused by authorities' efforts to destroy the package and render it safe.

Pacheco says there was no threat to public safety.

The package was found after a shooting rampage that left Giffords wounded and killed six others.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

TUCSON, Ariz. (AP) — A loud noise rattled more than 100 people attending a candle light vigil on Saturday near the headquarters of Rep. Gabrielle Giffords, where authorities were investigating a suspicious package hours after she was wounded in a shooting rampage in Tucson.

Police department spokesman Lt. Fabian Pacheco said an officer checking Giffords' office had found "a real strange" device that he said resembled a coffee can and had writing on it. Pacheco would not disclose what the writing said. A bomb squad had been working to render the device safe before the loud noise was heard.

Authorities did not immediately say whether the noise was caused by contents within the package or from authorities' efforts to destroy the device and render it safe.

"It's been a horrible and tragic day," he said. "The prudent thing for us is to take everything seriously."

Earlier Saturday, Giffords was holding a forum for constituents when the violence erupted, killing six and wounding several others, including the Democratic congresswoman.

Pacheco said there was no threat to public safety.

At the candle light vigil held, people huddled in the cold, held candles and read signs that said "Peace," and "Just Pray."

"She's just a great person," said Margaret Robles, 64, a retired teacher's aide who knew Gifford's grandparents. "She didn't care what color, what race, if you could read or if you were a scholar. She treated you as an equal."

Pima County Sheriff Clarence Dupnik gave few other details about the possible package.