South Shields Metro station was sealed off this morning after a worker was assaulted.
Police and paramedics are currently in attendance and a 20-year-old man has been arrested at the scene.
A Nexus spokesman said the staff member required hospital treatment.
Nexus later said the station had fully reopened and services were running as normal.
A Northumbria Police spokesperson said: “At 10.54am today (Monday), police were made aware of a disturbance at South Shields Metro Station.
“It was reported that there had been a disagreement between a male staff member and a passenger, which saw both fall to the ground.
“As a result of the altercation, the staff member suffered chest injuries and has been taken to hospital. They are not thought to be life-threatening at this time.
“A 20-year-old man has been arrested on suspicion of affray and is currently assisting officers with their inquiries.
“Anyone with information is asked to contact police on 101 quoting reference 298 101218 or Crimestoppers anonymously on 0800 555 111.”
Police were called shortly before 11am to the incident on the platform above King Street.
A Nexus spokesman said: “A male member of our customer service team was assaulted by a man at South Shields Metro station just after 11am.
“The police were called and the assailant was arrested at the scene. One member of our staff has since been taken to hospital for treatment.”
One eyewitness said: "I saw a lot of police around the station and up on the platform.
"They've got it closed off. Nobody knows exactly what has happened but it looks quite serious."