WASHINGTON (AP) — Federal officials are recommending that Washington’s subway system immediately repair components that are designed to protect the electrified third rail from water and other contaminants.

The National Transportation Safety Board issued the recommendation on Monday. The NTSB uncovered the problem while investigating a malfunction that caused a Metro train to fill with smoke. One passenger died and more than 80 others were sickened during the January malfunction.

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The NTSB says it has found electrical connections intended to protect the third rail elsewhere in the Metro system are either missing or were built and installed incorrectly. Water or dirt on the third rail can lead to smoke and fire. Metro says it will start installing hundreds of the components immediately.

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The NTSB has not determined the cause of the January malfunction.

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