At about 3pm on Friday a fire broke out in the exchange in Tumut that caused "significant damage to communications infrastructure", a NSW Police statement said.

"Police were called, and an investigation was commenced by officers from Riverina Police District.

"Meanwhile, later in the day three vehicles were damaged by fire on Lambie Street, Tumut.

"Police were called, and a description was given of a man who was later arrested by officers on Adelong Street."

The man was taken Wagga Police Station before being taken to Wagga Base Hospital for treatment to an existing health condition.

"He is expected to be charged with a number of offences including malicious damage by fire and break, enter and commit serious indictable offence later (on Saturday)," a police statement said.

"As a result of the fire, telecommunications infrastructure in the Tumut area has been significantly damaged.

"Technicians are working to restore communications as soon as possible.

"Where possible, listen to local radio stations for regular updates and advice."

Riverina Highlands RFS, whose main office is in Tumut, posted on Facebook on SAturday morning that Telstra and the National Broadband Network were sending emergency equipment.

"Tumut phone exchange fire. Telstra are deploying temporary mobile infrastructure which should be in place sometime today which should restore mobile services in Tumut," the RFS stated.

"NBN are also deploying a mobile wireless hotspot unit to be set up in Tumut CBD to allow basic internet when near its location.

"Fixed line services will still take some to restore. Please be patient."