After 42 years of service around Washington’s monuments and attractions, Tourmobile will make its final laps around the area on Monday, and it’s not clear when another service will start hosting the guided tours.

Tourmobile said on its Web site that it “will cease all tour operations on Monday, October, 31,” and the National Park Service issued a statement noting “conclusion of Tourmobile service” on that date.

The National Park Service announced in August that it was unlikely to renew its contract with Tourmobile, and Park Service spokesman Bill Line said Friday that the sightseeing bus company was in “tough straits” financially. On Sept. 1, the company told its workers that Tourmobile would cease tour operations on Monday, although its contract does not expire until Dec. 31.

But the Park Service did not officially open the process of seeking a new operator or operators until Friday, Line said. He added that he hopes the agency can choose a new company within two weeks.

Line said the agency is seeking buses whose operators can provide “interpretive services of the highest quality.” In recent years, Tourmobile has served about 700,000 to 800,000 people a year, at $32 a person.

Tourmobile began in 1969 as a subsidiary of Universal Studios and was launched with just three buses, the Park Service said in a statement. Recently, according to the bus company’s Web site, it employed almost 300 people and had a fleet of about 45 passenger vehicles. The company also provided tours of Arlington National Cemetery.

“This is a bittersweet time for the [Park Service] and Tourmobile, as they have faithfully served the needs of millions of visitors for over 42 years,’’ Steve Whitesell, regional director of the Park Service’s national capital region, said in a prepared statement. “Times change, and we are ready to enter a new era for visitors to access our national parks in Greater Washington.”

Steve Blakenship, a security consultant from Kinnear, Wyo., said he takes full advantage of the Tourmobile during his visits.

“I don’t want to drive in the bad traffic here, so this is a great service,” he said as he stood at a shuttle stop at Constitution Avenue and 21st Street NW, enjoying a hot dog from a local street vendor. “I would think most people would pay for the convenience.”

The Park Service is still considering whether to expand ways to tour around the Mall, including streets controlled by the Park Service. The possibilities include bikes, pedicabs and Circulator buses.

Tourmobile officials did not return phone calls Friday seeking comment. But on its Web site, the company held out the possibility that it would resume some operations. “We are currently unable to provide any information regarding future tour services, however, we will update our website as it becomes available,’’ the site says.

Tourmobile will run until 6 p.m. Monday.

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