The missing fiancé of Gabby Petito from the USA, who was killed under unexplained circumstances, is now being searched for with an arrest warrant.

Wyoming authorities issued an arrest warrant for 23-year-old Brian Laundrie on Thursday for suspected credit card fraud. 

The arrest warrant allows Laundrie's arrest while the FBI and other investigators across the country "continue to investigate the facts and circumstances of the murder of Ms. Petito," said FBI investigator Michael Schneider on Thursday (local time).

The police have been looking for Laundrie under high pressure for days.

So far he is officially only considered a “person of interest”, not a suspect.

The search is focused on a swampy area in Florida where the 23-year-old allegedly wanted to hike.

Every piece of information counts

The FBI asked again on Thursday for information from the population about Laundrie's whereabouts.

All vacationers who visited Spread Creek Campground in Wyoming at the end of August should also get in touch.

"No scrap of information is too small or too insignificant to report," said FBI agent Schneider.

The body of 22-year-old video blogger Petito was found in a national park in the US state of Wyoming on Sunday.

According to forensic medicine, Petito was the victim of a homicide.

The case has been moving the US for weeks and has also made headlines internationally.

Petito and Laundrie, who lived together in North Port, Florida, set out on a trip across the United States in July in a van converted into a motorhome.

They shared their experiences on the adventure, which was planned for four months, on the online services Instagram and Youtube, pictures showed a smiling couple and impressive landscapes.

According to police, Laundrie returned to North Port on September 1 with his girlfriend's vehicle - without Petito.

Her family finally reported the 22-year-old as missing on September 11th.

The 23-year-old initially refused to testify after returning to Florida and finally disappeared last week.