MINNEAPOLIS -- Federal investigators looking into last week's bridge collapse in Minneapolis say there is a possible design flaw and issued a national alert for other bridges.
The National Transportation Safety Board said at a news conference Wednesday one of the avenues of its investigation was the design of steel connecting plates known as gussets, the Minneapolis Star Tribune reported Thursday.
The NTSB said it was also looking into the weight of sand, gravel and construction vehicles on the Interstate 35W bridge last Wednesday when it fell into the Mississippi River.
The board's alert told bridge engineers nationwide to "carefully consider the additional weight placed on bridges during construction or repair projects."
Elsewhere, Minneapolis Police said 16 people have been arrested for trespassing at the cordoned off site. Capt. Mike Martin told reporters the area is considered a death-scene investigation site, and the state Department of Transportation is assuming control for security, CNN reported.
Five people were killed in the collapse, five others are in critical condition, and eight people remain missing.
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