SINGAPORE - For a fleeting moment on Monday, motorists in the 16-month-old Marina Coastal Expressway (MCE) may have thought the partly-undersea road had sprung a major leak.
But the water that descended in a torrent from the tunnel ceiling was actually from the MCE's deluge system - essentially an oversized fire sprinkler system that dispenses 350 litres of water a second.
The sudden downpour caused traffic to slow down dramatically, as wipers and lights went on.
The Land Transport Authority said on Tuesday that a contractor working in the tunnel had "accidentally triggered" the system at around 12.15pm, along a westbound stretch of the MCE after the exit to Central Boulevard.
"There was no fire within the tunnel," an LTA spokesman said. "Based on our investigation, the system was accidentally triggered by a contractor who was undertaking cleaning and maintenance work on tunnel wall cladding."
He added that traffic was diverted out of the tunnel for around two minutes as the deluge system was turned off, just to be safe. Normal traffic resumed afterwards.
Rumours spread on social media that a leak had sprung in the tunnel and the MCE was closed.
The MCE, which joins the East Coast Parkway, Kallang-Paya Lebar Expressway and Ayer Rajah Expressway, has five lanes in each direction.
At its deepest, it is 25m below sea level. It is also the first undersea road in Singapore, with a 420m section beneath the seabed south of the Marina Barrage.
The 5km, $4.3 billion infrastructure is also the shortest highway here, and the costliest, at $860 million per km.