Technical glitch at NYSE Arca derails ETF auctions, sends traders scrambling

New York

NYSE Group sowed confusion among traders after a technical error hobbled one of its exchanges on Monday, wreaking havoc on hundreds of exchange traded funds (ETFs).

NYSE Arca, the largest US listing venue for ETFs, left traders scrambling at the end of the trading day after a system upgrade went awry. An upgraded version of its software that went live on Monday derailed closing auctions for certain securities, a key moment at the end of the trading day.

The exchange shifted to backup methods for calculating the closing prices for most names, and went back to using an old version of its software, according to an e-mail to clients. A total of 341 symbols did not complete their …