The soldiers seemed out of place in paradise.
They stood guard at the sandy entrances to the exclusive, beachside hotels, holding their guns while inspectors took careful measurements and studied documents.
Tourists from around the world sauntered by on their way to spa treatments or sunned themselves on private decks overlooking the Mexican Caribbean's blue-green waters, puzzled but mostly unconcerned.
Until Monday, when the soldiers returned with federal officials who slapped "closed" signs across the hotel entrances and said they would be back on Friday to start clearing out guests.
The federal government's closure of five small, exclusive hotels on Tulum's breathtaking stretch of white-sand beaches has created an uproar over who has the title to one of the few still-to-be-fully-developed coastlines left along the exclusive Riviera Maya. At least five other developments near Tulum's seaside Mayan ruins are also under investigation.
The actions carried into Thursday, when the federal Environmental Department announced it had shut down construction of an Acapulco development that didn't meet environmental standards.
Visitors driving south from Cancun find most of the coast has been divided up and sold off to hotel chains. There are monster, all-inclusive resorts boasting hundreds of rooms and a maze of swimming pools, as well as sprawling communities of vacation villas and beach clubs.
Then there is Tulum, a tiny hippy-style town that started as a backpacker retreat. Most hotels were a collection of primitive thatched huts stuck into the sand and surrounded by beachside jungle.
But it has recently transformed itself into a chic eco-resort, one where travelers pay up to $500 a night to practice yoga on the beach and stay in minimalist Mayan suites where flatscreen televisions and iPod docking stations are powered by solar energy.
Title disputes have haunted the Tulum beach for decades. At the heart of this dispute, however, is whether the hotels were built in a federal park.
Federal environmental prosecutor Patricio Patron says the land is protected and the government wants to eventually demolish the buildings and leave the area untouched. But he says bulldozers won't arrive for a year or more as the cases work their way through Mexican courts.
John Kendall, owner of Mezzanine, a 10-room resort featuring a beachside restaurant and bar, says the federal government just wants to take back land that is worth millions of dollars.
"The pretext is totally fabricated," he said.
Ari Kantrowitz, a New York City graduate student, said he and his girlfriend were in the pool Monday when two bureaucrats walked up, carrying clipboards and signs that said "closed" in Spanish.
"Suddenly, walking behind them were four guys in full fatigues, helmets and carrying M16 rifles. It was somewhat surreal," he said. "We sort of just sat in the pool ... After a bit, I assumed it was the Mexican government and not some rogue militia."
Kendall has held nightly meetings with his guests, assuring them that he will find alternative lodging if they are forcibly evicted on Friday.
But guest Richard Beaver and his wife aren't waiting to find out what happens. The couple from New Zealand plan to check out first thing Friday. They drove up Monday as soldiers and government officials were posting the closed signs.
"There were guys walking around with big guns, and my wife didn't want to stay," he said. "We thought we had come to a really nice place, but to look at that was pretty intimidating."
Patron says officials will let guests stay until they are scheduled to leave, even if it means they stay past Friday. But he warned the hotels against taking on new clients.
He says the developments have yet to show adequate titles, are too close to the Mayan ruins and are built in an area for protected plant and animal species, including the towering chit palm.
"We are forced to comply with the law," he said.
Hotel owners argue they've been there for up to two decades without problems, and their businesses are built around protecting the environment.
Roberto Palazuelos, a Mexican soap opera actor and president of the Tulum Hotel Owners Association, says the federal government's paperwork to create the protected area in the 1980s was never done correctly. His Hotel Diamante K is among the five that have been closed.
"I think they want to take away the land and divide it between themselves," he said.
The state government issued the land titles and says they are valid. Tourism officials have been visiting the hotels this week and supporting their fight to keep their land.
In the meantime, urban refugees seeking peace and quiet in Mexico's jungle squeeze in one last spa treatment and wonder when the soldiers will return.