Lennox-Fruchtmann, 22, and Ian Jones, 32, were kayaking in the Hudson River near the Staatsburgh State Historic Site when they capsized at about 9:30 a.m., Dutchess County Sheriff's Captain John Watterson says.
While the cause of the capsizing is still under investigation, Watterson says they believe both the river's strong current and alcohol may have played a role.
"The current in the Hudson River is very strong and we believe the current played a role in the kayak capsizing, and once the two got in the water it was difficult for them to stay together," Watterson says.
Lennox-Fruchtmann was picked up by a passing vessel, he says. The sheriff's office responded to the scene at about 9:50 a.m. local time.
Watterson says more than 50 people were involved in the first day's search that went until 10 p.m. Saturday – as a helicopter scanned the area from above and searchers walked the shore – before resuming at 7:30 a.m. Sunday.
The Sunday search involves both Marine patrol and a dive team, Watterson says.
Lennox-Fruchtmamn, an artist, and Jones, a photographer and model, documented their relationship on their Instagram accounts.
Lennox-Fruchtmann, who was evaluated at the scene Saturday and did not require treatment, was on-hand for much of the first day, Watterson says, and is being kept updated as information becomes available.
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"We're doing everything we can to find him," Watterson says. "We hope to find him alive and well."
Representatives for Lennox did not immediately respond to a request for comment from PEOPLE.
Jones is described as a white male with dark hair, 6 foot 3 with a slim build, wearing jeans and a denim shirt.
Anyone with information is urged to contact the Dutchess County Sheriff immediately, at 845-486-3800 or 845-605-CLUE (2583), or by emailing firstname.lastname@example.org.