The crew of the International Space Station was forced to evacuate the U.S. side of the station today, January 14, following what might have been a toxic ammonia leak. The crew is now on the Russian side of the station. NASA now believes that there was probably not a leak, but they are looking into the situation more to make sure.

On the ground, at around 4 a.m., Mission Control noticed pressure changes that indicated a possible ammonia leak on the U.S. side of the station. NASA said in a tweet that the leak is starting to look like a false indication, but that they are coming up with a plan to make sure the astronauts remain safe.

"We saw an increase in water loop pressure, then later saw a cabin-pressure increase that could be indicative of an ammonia leak in the worst case scenario, so we protected for the worst case scenario and isolated the crew is the Russian segment of the space station while the teams are evaluating the situation," said Bob Jacobs, a NASA spokesperson.

Fortunately, the Russian and American mission control teams were able to work together on Earth to help protect the astronauts. The two American astronauts evacuated to the Russian side of the station, closing the hatch behind them.

"The safety of the team was preserved thanks to swift actions of the cosmonauts and astronauts themselves and the team on the ground in Moscow and Houston," said Maksim Matyushin, the head of Russian mission control.

In a tweet at about 8 a.m., NASA announced that there were no signs of a leak. NASA will be hosting a talk about the incident at 11 a.m. Eastern time on NASA TV.

Now that the crisis has passed, Mission Control told the ISS crew to enjoy the rest of the day off.