Apparent bomb threats were received at the Ottawa International Airport and airports across the country. Police are investigating. Federal officials have delivered an all-clear after air traffic control facilities at six Canadian airports, including Ottawa’s, received bomb threats Thursday morning.

Ground stops were lifted at international airports in Ottawa and Montreal after a bomb threat on Thursday briefly halted departing flights, a US Federal Aviation Administration (FAA) spokesperson said.

Several major Canadian airports have delayed and halted flights after receiving bomb threats, according to the country’s air traffic authority.