And now we know why

Source: Sydney Morning Herald
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It must have been a terrifying moment for visitors to the world's tallest tower, which only opened last month.
They heard what sounded like a small explosion, then saw dust that looked like smoke seeping through a crack in an elevator door 124 floors above the ground.
Inside an elevator, 15 people were trapped for 45 frightening minutes until rescuers managed to pry open the doors.
Outside on the observation deck, about 60 more people were stranded and some began to panic.
Shortly after the drama unfolded on Saturday evening, the half-mile-high tower that was supposed to be one of Dubai's proudest achievements shut down to the public one month after its grandiose opening.
It was the latest embarrassment for the once-booming Gulf city-state that is now mired in a deep financial crisis.
Witnesses who were on the 124th floor observation deck at the time and a Dubai rescue official recounted on Tuesday the chain of events that led up to the shutdown.
Emaar Properties, the state-linked company that owns Burj Khalifa, has said little about the incident and nothing at all about an elevator malfunction.
It had no comment on Tuesday. It remains unclear what caused the elevator to the observation deck - the only part of the building that was open - to fail.
Michael Timms, 31, an American telecommunications engineer who lives in Dubai, was on the observation deck with his cousin Michele Moscato when the ordeal began.
"It almost sounded like a small explosion. It was a really loud bang," Timms said.
About 45 minutes later, rescue crews arrived and pried open the elevator door, he added. The faulty elevator was caught between floors, so rescuers hoisted a ladder into the shaft to help those trapped inside crawl out.
Abu Naseer, a spokesman for Dubai's civil defence department, confirmed the incident. He said the call for help came in about 6.20pm on Saturday evening.
Emergency crews used another elevator to reach the observation deck and were able to rescue all 15 people stuck in elevator unharmed, he said.
Emaar, which owns the 2717-foot (828 metre) building, has not responded to specific questions about the incident.
Local newspapers reported the shutdown of Burj Khalifa on Monday but it is still not clear exactly when the building was closed.
The company issued a brief statement on Monday saying the viewing platform was temporarily shut for "maintenance and upgrade" because of "unexpected high traffic".
It also hinted at electrical problems, saying "technical issues with the power supply are being worked on by the main and subcontractors".
Emaar has made no mention of problems with the elevators, angering some of those involved in the incident.
"What just kind of shocks me is that they were going to brush this under the rug to save face. If it broke, at least tell people it broke," Timms said.
"I was really starting to get upset, getting really nervous," said Moscato, 29, a nurse visiting from Columbia, South Carolina. "I started crying."
She said she and Timms - along with other visitors, some in raised voices - asked to use the stairs because they felt uncomfortable taking the elevator back down, but were told that was not allowed.
Moscato said one of those trapped in the elevator told her later that the lights went off and the car began to fall before the brakes kicked in. It was not possible to independently verify the account.
The $1.5 billion ($1.7 billion) Burj Khalifa opened with a lavish fireworks display and other celebrations on January 4 after being beset by a series of delays.
Only the observation deck was being used for now as work continues on the rest of the building's interior. The first tenants were supposed to move in this month.
The tower more than 160 stories, though the exact number is not known. The tapering, silvery tower ranks not only as the highest building but also as the tallest freestanding structure in the world.
The observation deck, which is mostly enclosed but includes an outdoor terrace bordered by guard rails, is located about two-thirds of the way up.