Please, sir, do not throw your toilet out the window, no matter what the stranger on the phone is telling you.

If the phone in your hotel room rings unexpectedly at 2 in the morning, you might soon become the next victim of a network of scammers who are causing tens of thousands of dollars in damage at accommodations around the country.

Often imitated and deviously duplicated, a group called PrankNET appears to be at the center of a growing trend that has harried hoteliers and restaurateurs for months and is now being investigated by the FBI.

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The head of PrankNET, who goes by the online name "dex" and has been behaving badly since 2000, leads an online chat system where he and fellow merry pranksters collaborate. Members of PrankNET chat online, stream their calls live on an Internet radio show and post their greatest hits to a YouTube page, a popular breeding ground for more pranks.

During their calls they often drop the name of a security corporation or say they are phoning from a hotel's front desk to lend themselves an air of credibility — and to get their victims to do surprising things.

In February, Dex's work made headlines when he called a KFC in Manchester, N.H., and convinced workers there to douse the restaurant with fire suppression chemicals, evacuate the building and strip outside in freezing temperatures. Dex accomplished all of this by pretending to be their boss from a corporate office.

Calls recently posted to PrankNET's YouTube channel have upped the ante even further, capturing scenes where confused hotel patrons have been duped into setting off fire alarms and sprinkler systems — flooding hotels and panicking sleeping guests.

A Florida family staying in an Orlando Hilton was tricked last week into smashing windows, breaking a mirror, bashing in a wall with a lamp and tossing their mattress outside, causing about $5,000 in damage, the Orlando Sentinel reported. The caller persuaded them to do all of that in order to save themselves from a gas leak.

The sheer difficulty of tracing prank calls placed online, and the social-networking programs used by pranksters, has increased their visibility and daring. Last week, a North Carolina teenager was indicted in federal court for allegedly phoning in bomb threats to colleges and universities — and taking payments to threaten specific high schools, canceling classes for anyone who'd put $5 into his PayPal account.

Another couple was called on PrankNET recently by someone claiming to be from their hotel front desk who told them that "deadly" exotic spiders had escaped and were going to swarm their hotel room. In order to avoid that catastrophe, they had to shatter their windows with the top of their toilet tank. After a few tries, they succeeded. Crisis averted.

That post was hidden by PrankNET following a FOXNews.com inquiry, even as the administrator of its YouTube page told FOXNews.com that "copycats" were to blame for many of the pranks in the news.

Though the perpetrators in many of these cases remain unclear, PrankNET's administrator took direct credit for at least one prank:

In York, Neb., a Hampton Inn employee was tricked into setting off an alarm and then was convinced that the only way to make it stop was to break the hotel's windows. He enlisted the help of a trucker who smashed his vehicle into the front door, shattering the glass and causing more than $1,000 in damage.

The owner of PrankNET's Twitter account — believed to be Dex — claimed in a post the night of the incident, "I just pulled off the most epic prank. I had a hotel guest back his truck into the hotel front window (in the lobby), and break the window." That post, too, has been deleted.

A small community of prank callers have long enjoyed Dex's work, but some are growing concerned over his increasingly destructive ends.

"While I can't help finding Dex's calls extremely amusing, I think that they need to stop before he seriously hurts or kills someone," said Brad Carter, who runs the Web site phonelosers.com and has been following Dex's activity.

"I'm amazed that nobody has hurt themselves yet by breaking these giant plate glass windows [at hotels]. I'm amazed that he's still making all of these calls when he knows the FBI is investigating them and he's probably caused millions in damages at this point."

The FBI's field office in Knoxville, Tenn., is looking into possible revelations of Dex's identity following an incident that caused an estimated $50,000 of damage at a Holiday Inn Express in Conway, Ark. An employee there was convinced to set off the fire alarm, shatter front windows and bash off a sprinkler head, which set off the sprinkler system and flooded the hotel.

A Knoxville woman named Jericho Batsford contacted the FBI's field office in Knoxville and said she knew Dex's identity and confirming that he was responsible for the Conway call and many others, according to the Log Cabin Democrat of Arkansas.

Batsford, who could not be reached for comment, told the newspaper that she used to pull similar pranks herself. Some videos circulating online among prankNET members show someone identified as Dex, though their accuracy could not be confirmed.

Despite this string of incidents, an FBI official in Washington said the pranks do not represent a trend. "They're looking into it [the incident at motel], but it's not a widespread thing," said a bureau source. The FBI's Internet Crime Complaint Center has received just one complaint stemming from the incidents.

But cybersecurity experts say such attacks are dangerous and may be on the rise.

"It can be very serious for the people who are being attacked," said Parry Aftab, a cyber law expert. "It hasn't become a systemwide abuse ... but it will increase as more people get ideas on how to do these kinds of things."