ORANJESTAD, Aruba -- About 700 volunteers joined police, soldiers and FBI agents, combing scrubland and beaches on Aruba's southeastern tip in a search for Natalee Holloway.

The 18-year-old Alabama woman vanished a week ago while on a graduation trip.

Aruba authorities called on government workers and tourists Monday to join law enforcement in a massive search of the island for the missing woman. The government announced on the radio that civil servants could take time off to help look for Holloway. It also asked the FBI to send a dive team to search the rough currents around the island.

This came the day after authorities arrested two security guards from a hotel near where Holloway was staying. Police searched the men's homes and came out carrying what looked like a metal safe deposit box and a garbage bag of clothing.

Aruba Attorney General Caren Janssen wouldn't say what charges the men face, but said officials didn't find any of Holloway's belongings at the suspects' homes. Police said the FBI is helping with forensic tests.

Janssen did say, "The charges have a relationship with the disappearance" but would not elaborate. She said the pair will appear before a judge by Tuesday.

ARUBA FACTS LOCATION: An island in the Caribbean Sea, north of Venezuela POPULATION: 71,566 GOVERNMENT: Part of the Netherlands LANGUAGE: Dutch ECONOMY: Tourism, offshore banking INTERACTIVE: World Factbook Map

The arrests came nearly a week after Holloway disappeared during a five-day trip to Aruba with more than 100 other classmates from Mountain Brook High School, near Birmingham, Ala. Her passport was found in her hotel room after she disappeared.

The men -- ages 28 and 30 -- were arrested Sunday morning at two separate homes in the southeastern community of San Nicolas.

Police said they have not ruled out the possibility other people were involved in her disappearance. And the police chief added: "We hope she's alive."

Meanwhile, Holloway’s aunt is relieved a blood-soaked mattress found on a beach in Aruba apparently was not related to her niece's disappearance.

Authorities said the blood is from a dead dog found nearby -- not from Holloway. Marcia Twitty said, "Thank God it wasn't Natalee."

She said even though it's another dead end in the case, she wants everyone to keep praying and keep searching for her niece.

Twitty, whose twin 17-year-old boys were on the same trip to Aruba, said Natalee's disappearance makes her love her own children that much more.

Prayer Vigil Held

At least 70 people have attended a prayer vigil in Aruba for Natalee Holloway.

They sang a hymn and listened to a brief sermon by an American minister who now lives in Aruba.

He said the so-far unsuccessful search for Holloway is a trying time "for the world as a whole."

Holloway had been visiting the island with classmates to celebrate their high school graduation.

A reward of $50,000 is being offered for information leading to her rescue.

Holloway was active in many clubs in school, including the dance squad and the Spanish Honor Society. She was also on the honor roll in the 10th through 12th grades. She is expected to attend the University of Alabama on an academic scholarship this fall.