Canada's largest school system is calling off all future trips to the United States, citing uncertainty over President Trump's travel ban.

The Toronto District School Board announced Thursday that no student or staff outings south of the border would be booked until further notice, saying it wasn't clear when the restrictions would come into effect.

Canada isn't named in the ban, but the board expressed concerns that some of its students would face trouble on U.S.-bound trips, even if they had the proper paperwork. The district serves about 246,000 students and includes nearly 600 schools throughout Toronto, home to one of Canada's largest immigrant communities.

"We strongly believe that our students should not be placed into these situations of potentially being turned away at the border," Director of Education John Malloy said in a statement.

Toronto District School Board says no more school trips to U.S. after recent immigration and refugee travel bans issued by President Trump. pic.twitter.com/4vPpWHtkWe — Spectrum News ROC (@SPECNewsROC) March 24, 2017

"We will continue to monitor this situation very closely and should we receive additional information or clarification with regards to what students could expect at the U.S. border, we may revisit these decisions," he said. "However, based on all the information we currently have available to us, we feel this is the right action to take at this time."

Trump unveiled his first executive order restricting travel from seven Muslim-majority countries in January. After sparking widespread protests and creating confusion for untold numbers of foreigners, the order was blocked by federal judges at the request of several states that challenged it in court.

The administration issued a revised ban in February seeking to bar nationals from six Muslim-majority countries from obtaining visas to the United States and suspend the admission of new refugees. That order has also been temporarily frozen by federal judges, who said it appeared to discriminate against Muslims specifically.

The Toronto board said 24 already-approved trips involving about 800 students would proceed as planned, though it warned that if U.S. authorities turned away any students with appropriate documentation, the entire group would return to Toronto.

"We just can't have trips going across the border and a student for no legitimate reason being denied entry to the U.S.," Ryan Bird, a spokesman for the board, told the Associated Press. "We're obviously not going to leave that student and continue on."

With a population of 2.6 million people, Toronto is home to 30 percent of Canada's recent immigrants, according to the city's website. In 2006, half of Toronto residents reported being born outside Canada. In 2013, it became the first Canadian city to declare itself a sanctuary city, allowing undocumented immigrants to live, work and access services there, although a recent report questioned whether it could truly claim that status.

Toronto joins other school districts and Canadian groups in canceling trips to the United States over concerns about Trump's travel ban.

The Greater Essex County District School Board of Windsor, Ontario, suspended field trips in February, citing uncertainty over Trump's initial executive order, as The Washington Post's Amy Wang reported. The board's worries mirrored those expressed by Toronto school officials Thursday.

"Paramount for us is student safety," Clara Howitt, a school board superintendent, told the Windsor Star last month. "We really don't know what will happen to our students at the border."

In a separate interview with the Detroit Free Press, Howitt said canceled trips included one to watch "The Lion King" at the Detroit Opera House and to the Holocaust Memorial Center in Farmington Hills, Mich.

Essex County's school board in southwestern Ontario canceled several trips in February, and the Ottawa-Carleton District school board sent a letter to parents asking parents whether their children would take part in planned trips to the United States, according to the Associated Press.

Just last week, Canada's Girl Guides – the Canadian version of the Girl Scouts – canceled all future U.S. travel, citing their "commitment to inclusivity." They stopped short of mentioning the travel ban specifically, but the move was widely interpreted as a stand against Trump's executive order, as The Post's Brian Murphy reported. Among the canceled outings was a summer camping trip in California.