This is what Shell stated about it:
"As a result of a mechanical issue at one of our olefins units, we are experiencing steam issues at the Norco site. As a result we had to shut down several Shell and Motiva units at the site to reduce the environmental impact of flaring and to maintain the operation of our larger units. We will experience elevated flaring for several days during the restart of the units. "
They also stated that there was no danger to the community.