Maine’s U.S. senators are pushing for greater security along the Canadian border.

A measure aimed at strengthening the 5,500-mile border recently passed the U.S. Senate without dissent and is now in the hands of the U.S. House, which may act before the current session ends next month. It has already backed a similar bill.

“Maine law enforcement officers and Border Patrol agents are the first line of defense in maintaining the security of our border with Canada and protecting Maine from threats,” said Maine’s two senators, Susan Collins and Angus King, in a joint statement.

They said the proposal they co-sponsored would help officials understand “the northern border’s needs, strengths and vulnerabilities.”

The Northern Border Security Review Act “will play a significant role in bolstering our border security, supporting law enforcement and keeping Maine citizens safe,” Collins and King said in the statement. Maine’s border with Canada is 611 miles, nearly all of it sparsely populated.

The Congressional Budget Office estimated the bill would cost about $1 million to implement and would not have any impact on state or local spending.

A 2015 report from the Senate Homeland Security and Governmental Affairs Committee found that about 5,700 Border Patrol and other federal officers are posted along the Canadian border.

But, it said, “Due to the large size of the border and the relatively small number of agents patrolling it, drug smugglers and other traffickers have been able to move illicit goods across the northern border in both directions. For instance, cocaine from South America travels north across the United States to the U.S.-Canada border, while ecstasy and marijuana flow south to U.S. markets from Canada. Sometimes the two are traded directly, in integrated ‘double exchanges.’”

The report also said guns, cigarettes and other goods are shipped across the border illegally, and that undocumented immigrants are able to cross.

It said “some experts also believe that terrorists could exploit vulnerabilities along our northern border to carry out an attack on the U.S.”

With the rise of a terrorist pseudo-state in parts of Syria and Iraq and the ability of the Islamic State to recruit foreign fighters, the committee said, “The threat along our northern border has increased significantly since 2012.”

One of the measure’s sponsors, U.S. Sen. Heidi Heitkamp, D-N.D., said in a prepared statement that she sought to strengthen the cooperation between border security agents and local law enforcement officials.

“Keeping our country safe means making sure all of our nation’s borders — both north and south — are adequately protected to meet modern-day challenges,” Heitkamp said.

U.S. Sen. Gary Peter, D-Mich., said the border “is critical to our economy, allowing goods and travelers through some of the busiest border crossings in the nation.”

He said the proposal’s passage “will help protect the northern border and prevent criminal activity like human trafficking as we work to promote more efficient trade and travel to help grow our economy.”

The proposal would require the U.S. Department of Homeland Security to conduct a detailed threat analysis of the Northern Border Region, updating one finished in 2012.

It calls on the department to examine everything from terrorism to the cooperation required among border agents, tribal law enforcement and local police across the length of the border, including 120 formal entry points.

About 300,000 people and $910 million in trade cross the northern border daily, according to Collins and King.