2 sentences for 警戒线 (jǐng​jiè​xiàn — cordon)

1. 警察在事故现场周围拉起了警戒线。

   jǐng​chá zài shì​gù xiàn​chǎng zhōu​wéi lā​qǐ le jǐng​jiè​xiàn.

   Police cordoned off the scene of the accident.

   Source: Dong Chinese Dictionary

2. 警察已经在建筑物外围拉起了警戒线。

   jǐng​chá yǐ​jīng zài jiàn​zhù​wù wài​wéi lā​qǐ le jǐng​jiè​xiàn.

   The police have already set up a cordon around the perimeter of the building.

   Source: Dong Chinese Dictionary