US border officers working at multiple crossings with Canada were instructed to target and interrogate Iran-born travellers in early January, according to an email obtained by CBC News.

In the email, which was sent by an officer with the US Customs and Border Protection (CBP) to immigration lawyer Len Saunders, frontline staff were directed to ask Iran-born travellers counterterrorism questions.

When war drums beat for Tehran: Iranian-Americans on 10 days from hell Read More »

The officer, whose identity has not disclosed amid fears of repercussions from his employer, claimed that the sole reason travellers were detained and questioned was their ethnicity. He alleged that the operation was unethical and possibly unconstitutional.

On 4 January, more than 60 people of Iranian descent, some reports have suggested up to 200, were detained and questioned for hours at the Peace Arch Border Crossing in Blaine, in Washington state.

A day earlier, the US assassinated Iran's top general, Qassem Soleimani, intensifying tensions between the two countries.

In the email, the CBP officer said that after the detainment of Iranian-born travellers made international news, the operation was suspended.

He added that instruction to stop and detain travellers came from CBP's Seattle Field Office and covered the US-Canada border from Washington State to Minnesota.

"It confirms my suspicion that this was not just happening at Peace Arch," Saunders told CBC News.

"They violated American constitutional rights by interrogating them and detaining them," Saunders added. "What's next? Where does it stop?"

'Please don't speak Farsi'

Negah Hekmati, an Iran-born US citizen, said she and her family were held for questioning at the Peace Arch crossing for five hours after returning from a ski weekend in Canada on 5 January.

Iranian student held at Boston airport deported ahead of hearing Read More »

Hekmati told a news conference a day after the incident that her family had their passports taken and was placed in a room filled with other Iranian-Americans.

"My daughter was telling me, 'please don't speak Farsi. Maybe if you don't speak Farsi they won't take you,'" Hekmati said.

Since the incident, more that 70 members of US Congress sent a letter to CBP demanding answers.

CBP has denied reports that the agency has been targeting Iranian-Americans for extra questioning because of their backgrounds.

"Social media posts that CBP is detaining Iranian-Americans and refusing their entry into the US because of their country of origin are false. Reports that DHS/CBP has issued a related directive are also false," CBP tweeted at the time.

On Monday, an Iranian student who was detained by CBP at Boston airport was deported in an irregular move just hours before he was supposed to attend court proceedings.