In this Oct. 9, 2019 photo, traffic enters Canada from the United States at the Peace Arch Border Crossing, in Blaine, Wash…
FILE - Traffic enters Canada from the United States at the Peace Arch Border Crossing in Blaine, Washington, Oct. 9, 2019. More than 60 Iranians and Iranian-Americans reportedly were detained and questioned at the border crossing over the weekend.

Human rights groups and several U.S. lawmakers are demanding answers after dozens of Iranian-Americans were held for questioning at the U.S.-Canada border over the weekend, coinciding with a sharp rise in tensions between Washington and Tehran.

The Washington State chapter of the Council on American-Islamic Relations (CAIR-WA) said it assisted more than 60 Iranians and Iranian-Americans of all ages who were detained for as long as 11 hours and questioned by U.S. Customs and Border Protection agents.

In a statement, CAIR said all who were held have been released, but others were turned back at the Peace Arch Border Crossing in Blaine, Washington, and, at least temporarily, prevented from entering the United States. CAIR said many were returning home after attending an Iranian pop concert Saturday in Vancouver, Canada.

"These reports are extremely troubling and potentially constitute illegal detentions of United States citizens," said CAIR executive director Masih Fouladi in the statement.

The incident coincided with the U.S. Department of Homeland Security announcing it was increasing security at ports of entry following Iranian threats to retaliate against the United States for an airstrike Friday in Iraq that killed Tehran's top military leader, Qassem Soleimani.

U.S. Customs and Border Protection (CBP) denied any targeting of Iranian-Americans, tweeting: "Social media posts that CBP is detaining Iranian-Americans and refusing their entry into the U.S. because of their country of origin are false. Reports that DHS/CBP has issued a related directive are also false."

Federal officials cited slow processing times at the port of entry due to holiday season staffing shortages and heavy weekend border traffic. On Monday, CBP reported a five-minute wait time at the same port of entry for passenger vehicles.

Jorge L. Barón, head of the Northwest Immigrant Rights Project in Washington State, contested CBP's denial that people were detained, tweeting: "[T]his is only true if you define 'detain' to mean only to be placed in a locked room. These individuals were in a waiting area and could walk to the parking lot but were not free to go."

"They were not being allowed to enter the U.S. (their only home) and CBP was holding their passports so they couldn't [go] back to Canada even if they had wanted to. So yes, they were detained," he added.

Though U.S. border officers are not allowed to refer people for a "secondary screening" based only on national origin, both the New York Times and The Intercept reported that an officer told an Iranian-American family that "It's just a really bad time for you guys right now. Go ahead and pull to the side."

Members of Congress, especially those representing Washington State, are speaking out.

"Deeply disturbed by reports that Iranian Americans, including U.S. citizens, are being detained at the Canadian border with WA [Washington] State." Democratic Congresswoman Pramila Jayapal posted, encouraging those affected to contact her office.

Congressman Adam Smith, also a Washington State Democrat, said his office was seeking answers as to what happened at the border.

"It is unacceptable for the civil liberties of Americans and immigrants to be violated. We cannot let discrimination dictate our policies and actions," the U.S. lawmaker tweeted.

Over the weekend, DHS updated its National Terrorism Advisory System to warn of Iran's capability to retaliate against the United States through cyberattacks, violence by homegrown extremists, or terrorism attacks.

The bulletin system, which was last updated in July, is designed to assist law enforcement and the public to report suspicious activity.

CAIR said it will continue to monitor treatment at the border, noting that more Iranian-Americans are expected to return home through the same crossing.