A pit bull mix named Roo reunited with his owner after being trapped for two days inside a San Francisco Caltrain tunnel, according to Animal Care and Control San Francisco.

NBC Bay Area reported that Roo went missing shortly after being adopted, reportedly becoming frightened and running away.

According to the New York Post, early reports suggested the dog was dead because he remained motionless inside the tunnel. However, a Caltrain operator noticed that the animal move and alerted authorities, assuming the dog might be injured.

“The first day train operators saw him & thought he was a dead animal. The 2nd day a driver saw him move. He was so still they thought he had been hit by a train and was injured,” San Francisco Animal Care and Control (SFACC) said on Instagram.

 

 
 
 
 
 
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A post shared by SF Animal Care & Control (@sfanimalcareandcontrol)

Officers Pone and Borg from Animal Care and Control reportedly responded to the scene and rescued the dog, the agency said in their Instagram post. Roo was taken to SAGE Veterinary Centers for medical evaluation. Although he had gone without food or water and was unsteady on his feet, veterinarians said he was alive, uninjured, and simply terrified by the ordeal.

Deb Campbell described Roo’s reaction upon realizing that he was being rescued, saying, “First, he was terrified to see them. Then, he was absolutely thrilled and happy.”

“This is pretty unlikely. Typically, dogs do not like spending time around trains—they’re loud and scary, and they typically are not hanging out around them,” Caltrain spokesperson Dan Lieberman told The San Francisco Chronicle.

San Francisco Animal Care and Control’s post has garnered widespread attention, with many expressing relief about Roo’s rescue. A comment read, “Thank you to all involved, including the train operators who noticed him.” Another wrote, “That must have been so terrifying! Poor Roo! So glad to hear he is home now! Thank you for your great work.” A third noted, “Thank you to the crew who took the effort to rescue him! You are wonderful!”

Authorities noted Roo’s rescue highlights how difficult it can be to locate missing pets when they wander into unfamiliar and dangerous places, like active rail tunnels.

Speaking to KQED, Campbell also noted that Roo had been microchipped, but the chip had never been registered. “We get a lot of animals that have microchips, but nobody has gone and registered them,” Campbell said, adding that registering a microchip takes only a few minutes and could improve chances of quickly reuniting with the lost pets with their owners.