The FBI has released the first physical description of the man believed to have kidnapped Nancy Guthrie, the mother of US news anchor Savannah Guthrie.

Nancy Guthrie, 84, disappeared in the middle of the night from her Tucson, Arizona, home and was last seen two weeks ago. The authorities believe she was taken against her will.

The FBI has analysed footage from a doorbell camera outside her home and believes she was kidnapped by a male who is between 5ft 9in (175cm) and 5ft 10in tall, with an average build.

This is the first time the man in the video has been officially identified as a suspect in the case, which has drawn significant attention both in the US and abroad.

In its latest statement, the FBI said it had established identifying details after carrying out a forensic analysis. They highlighted the backpack worn by the suspect as a 25-litre Ozark Trail Hiker Pack.

A pair of black gloves has also been found during the search for Guthrie, CBS reported on Thursday.

Nancy Guthrie was last seen on the evening of January 31 when family members dropped her home. Members of her church noticed her absence at Sunday’s service and notified her family.

Officials have warned she may be in dire health without her medication. Pima County Sheriff Chris Nanos stated she was not in good physical health but had no reported cognitive issues.

Since February 1, the FBI said it had received more than 13,000 tips related to the case, including 4,000 in the 24 hours after the doorbell camera footage was released.

They are offering a reward for anyone who comes forward with information about her disappearance, which has now doubled to $100,000.

Earlier this week, a man was detained in connection with Guthrie’s disappearance. His home in Rio Rico, south of Tucson, was searched before he was released, saying he did not know who Nancy Guthrie was.

Savannah Guthrie and her siblings have made several social media pleas directed at their mother’s potential abductors, indicating they believe she is still alive and are willing to pay for her return.