Authorities are investigating a suspicious letter filled with a “white powder” substance sent to U.S. Ambassador to Canada Kelly Craft.

“An email sent to all embassy staff say the incident happened around 10:30 yesterday morning after an off-site mailroom supervisor ‘encountered white powder while screening a letter addressed to the Ambassador,’ Kelly Craft,” CTV News reports.

The package, sent to Craft’s residence in Ottawa, included a letter threatening to kill the 56-year-old unless she stepped down as Ambassador. The letter also included an expletive-filled rant against President Donald Trump.

The letter may have been sent from Quebec, the host province of the G7 Summit in Charlevoix held last week.

A spokesperson for the U.S. Embassy in Canada says the white powder tested non-harmful.

On Friday, Canada’s Foreign Affairs Minister Chrystia Freeland met with Craft and called the situation “wholly unacceptable.”

“Pleased to meet with Ambassador Craft today to discuss the value and strength of the Can-US relationship and the harmful impact of US section 232 tariffs,” Freeland tweeted. “I also expressed my support for the Ambassador following the wholly unacceptable threat made against her. She does an essential and difficult job and Canada respects her service.”

1/2 Pleased to meet with Ambassador Craft today to discuss the value and strength of the Can-US relationship and the harmful impact of US section 232 tariffs. @USAmbCanada pic.twitter.com/6gGW2Ah8nm — Chrystia Freeland (@cafreeland) June 15, 2018

2/2 I also expressed my support for the Ambassador following the wholly unacceptable threat made against her. She does an essential and difficult job and Canada respects her service. @USAmbCanada — Chrystia Freeland (@cafreeland) June 15, 2018

The incident follows President Trump ordering U.S. officials not endorse a G7 communique after accusing Canadian Prime Minister Justin Trudeau of making “false statements” on trade.