All four Sikh family members, including an eight-month-old baby girl, who were kidnapped in the US state of California earlier this week, have been found dead in an orchard, authorities said on Wednesday.

The family, originally from Harsi Pind in Hoshiarpur, Punjab, was kidnapped from their newly-opened trucking business in Merced County, California, on Monday.

Merced County Sheriff Vern Warnke said the bodies of 36-year-old Jasdeep Singh, 27-year-old Jasleen Kaur, their eight-month-old child Aroohi Dheri and the baby's uncle, 39-year-old Amandeep Singh were found on Wednesday evening in an orchard near Indiana Road & Hutchinson Road.

"Our worst fears have been confirmed," he said.

Warnke said that a farm worker near the orchard found the bodies and immediately contacted authorities.

All of the bodies were found close together.

"There are no words to describe the anger I feel," Warnke said during a press conference Wednesday evening.

"There's a special place in hell for this guy," he said about Jesus Manuel Salgado, the suspect, who attempted to kill himself.

"It's horribly, horribly senseless," he said.

Family members said nothing was stolen from the trucking company but that their relatives were all wearing jewellery.

Warnke had said that after the kidnappings, an ATM card belonging to one of the victims was used in Atwater, about 14 kilometers north of Merced.

Warnke said the kidnapper made no ransom demands in what he believes was a financially motivated crime.

Earlier in the day, the Merced County Sheriff's Office released a chilling new video showing the moment the family was kidnapped.

Jasdeep and Amandeep Singh came out of the business with their hands zip-tied together. Moments later, the video shows the kidnapper leading Jasleen and her 8-month-old baby, Aroohi, out of the building into a truck.

Salgado, 48, the person of interest, was taken into custody Tuesday afternoon and remains in the hospital in critical condition after he tried to kill himself.

The sheriff's office said his own family contacted authorities reporting that Salgado had admitted to them he was involved with the kidnapping of the family.

According to the Merced County Sheriff's Office, the investigation began on Monday at 11:39 am, when the California Highway Patrol responded to a 2020 Dodge Ram that was on fire and asked the Merced Police Department to help track down the vehicle's owner.

Roughly an hour later, at 12:35 p.m., Merced police officers arrived at the truck owner's address and met with a family member there. Officers tried to contact the couple and the child's uncle, but they were not able to reach them.

During the primary investigation, Detectives determined that the individuals were kidnapped, the sheriff's office stated on Tuesday.

The kidnapping involved a gun and restraints, according to Deputy Alexandra Britton, public information officer for the sheriff's office.

In an initial statement about the case Monday, the sheriff's office said it believed the family was taken against their will from a business in the 800 block of South Highway 59 in Merced, which sits between Modesto and Fresno in central California.

"We have no motivation behind it. We just know they are gone," Warnke said.

Investigators have not found a link between Salgado and the family to show they knew each other before the kidnapping.

Family members told KXTV-TV that the office for Unison Trucking Inc, the family's business, had only opened about a week earlier.