Thieves in Sweden walked into a small town's medieval cathedral in broad daylight and stole priceless crown jewels dating back to the early 1600s before escaping by speedboat, police said Wednesday.

Two men vanished after the noon heist Tuesday into a vast patchwork of lakes around Strangnas, 60 kilometers (37 miles) west of the capital of Stockholm, police said.

The thieves snatched two gold crowns and an orb made for King Karl IX and Queen Kristina in the daring robbery. One of the crowns is encrusted with precious stones. The stolen items were on display at an exhibition in the cathedral, and visitors were inside at the time.

"The alarm went off when the burglars smashed the security glass and stole the artifacts," Catharina Frojd, a spokeswoman for the 14th-century Strangnas cathedral, told The Associated Press.

The church wrote on its website that the stolen items were kept "in accordance with the prevailing safety regulations in locked and alarmed displays in the cathedral." It gave no further details.

Police sent out a helicopter and boat to hunt for the thieves but found nothing. Authorities said no one was hurt in the robbery, but didn't provide further details.

Tom Rowell, a visitor who was eating lunch outside, said he saw two men running from the cathedral toward a small nearby jetty where a motorboat was moored.

"The two men hurriedly jumped on board and it sped off," Rowell said, adding that they "appeared non-Nordic." He didn't elaborate.

The men appeared to have escaped using two black bicycles — which they likely stole ahead of the heist — to race to the waiting boat, said police spokesman Stefan Dangardt.

It was not immediately clear if there was a driver waiting in the speedboat for the thieves.

On Wednesday, divers were looking for clues in and along the shores of lake Malaren. Sweden's third-largest freshwater lake. Police said the thieves could have fled further on jet skis, adding it was only a theory.

While the items are of great historic and cultural value, police expressed doubt whether the burglary would bring the perpetrators financial gain.

The stolen items are "impossible to sell" because of their uniqueness and high visibility, Maria Ellior of the Swedish police's National Operations Department told the Swedish news agency TT.

The theft would be logged at Interpol, enabling an international search, TT said.

Strangnas is a small, quiet town with a population of about 13,000. It's popular with Stockholm commuters and tourists, who come to see the cathedral and a street that has been called the prettiest in Sweden.

The Gothic-style cathedral, built between 1291 and 1340, is in the heart of the town. The cathedral's red-brick tower with a black top can be seen from kilometers (miles) around.

The cathedral was closed Wednesday, and a grassy area by the jetty was cordoned off as police inspected the ground for clues. Police also questioned witnesses who were inside the church at the time of the theft and people outside who saw the suspects get away.

The stolen artifacts are funeral regalia, which are placed inside or on top of a coffin to symbolize a deceased royal's identity and social ranking.

While some funeral regalia are kept in the cathedrals of Strangnas, Uppsala and Vasteras, Sweden's crown jewels are in vaults of the treasury under the Royal Castle in Stockholm.

In 2013, 16th-century copies of King Johan III's crown, orb and scepter were stolen from the cathedral in the central Swedish city of Vasteras, 100 kilometers (60 miles) west of the capital Stockholm, during a nighttime burglary. They were eventually found and returned to the cathedral. No one was arrested.

Rowell, the witness, is getting married at the cathedral next weekend.

"It's despicable that people would steal from a holy building," he said.